OB cross top insulators ready for assembly for two differing style "stacker" units

The top skirt in the foreground with the metal cap was retrieved from an upstate New York swamp by Mike Spadafora last year. This is the only known survivor of this very large 17" diameter "monster" insulator. The swamp was probably the only reason it was not broken in the fall from the tower. See also [id=260298944] and [id=260297063] for more information on this massive insulator. Today, I had to tap the 3/4" hole on the extremely rusty top metal piece to receive the pin and M-4395 which goes on top (rear of photo). The OB stacker unit was apparently used at railroad crossings to reduce possible failure of the insulator due to electrical surges associated with a lightening strike on this "king pin" conductor (Most power lines of this time period were constructed with the three conductors in a DELTA triangular arrangement with the "king pin" position being the conductor on the top with the other two of the circuit on the bottom-left and right).

The 17" diameter "monster" insulator (for lack of a better term for it at this point) was apparently used only with the metal cap shown so it would have always had an M-4395 on the top. For this reason, it did not have a conductor groove or tie neck like it's cousin (M-4395). This was confirmed by finding other shattered insulators nearby which indicated that the metal cap did not hide a wire groove. The bottom three skirts of this monster insulator are the same as M-4395. Again see [id=260298944]. The top M-4395 cross top which screws into this metal bracket is shown at the rear of this photo. The two clevis attachments on either side of the metal cap (not shown curiously on the drawing) were obviously used for dead ending the conductor at the rail crossing if it was needed. In my opinion as an ex linemen, this would have produced significant side loading of the bottom insulator, particularly if there was a conductor failure on one side and not the other. Elton Gish says he wants to assign an M number to this insulator at some point.

Due to the height of the tandem OB stacker, there would have been considerable side leverage on the insulator arrangement so OB must have toyed with differing aggressive surfaces in between the cements used on the M-4395 cross top and 17" monster. At least two designs are seen in this photograph. On the left and middle, you can see that a course sand was fired into the top porcelain glaze interface to produce a good bond with the multipart cement. On the right, you can see this sand is missing and replaced with a circumferential fluting of the porcelain to add bonding mechanical strength. it was important that these M-4395 and monster insulators had excellent mechanical strength for side loading, particularly when used in tandem on the king pin position (especially over rail road tracks).

A second OB stacker constructed of two M-4395 (one on top of the other) was constructed using a triple-tined metal bracket made just for the top of the M-4395 just below the wire groove (in the flat recessed area). This bracket was fitted on the insulator using a copper mesh flat style rope to cushion it and keep from fracturing the top skirt and dropping the conductor. Several of these brackets exist in the hobby and I got mine from a collector in NY several years ago. For a photo of the second stacker unit, go to [id=169079359]. My daughter is standing next to the unit.

Currently, I am assembling all the components together for these 2 differing stacker displays. Once this is completed, I will post photos to ICON.

Reed Thorne Oak Creek Canyon Sedona, Arizona